Resiliently-coupled drive wheel assembly for self-propelled vacuum cleaner

ABSTRACT

A wheel assembly for a self-propelled apparatus such as a vacuum cleaner is disclosed. The self-propelled apparatus includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly. The drive wheel assembly includes a drive member rotatably secured to the drive axle, an outer wheel casing at least partially surrounding the drive member, and a resilient coupling mechanism for establishing a rotational engagement between the drive member and the outer wheel casing after a predetermined amount of rotation of the drive member relative to the outer wheel casing.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to wheel constructions. It finds particular application in conjunction with a resiliently-coupled drive wheel assembly for a self-propelled vacuum cleaner, and will be described with particular reference thereto. However, it should be appreciated that the wheel constructions disclosed herein can find use in a variety of other applications.

[0002] Self-propelled vacuum cleaners are well-known in the art. In a typical self-propelled upright vacuum cleaner arrangement, a transmission assembly associated with a floor nozzle assembly mechanically transfers rotational power from an electric motor to a drive axle. The drive axle supports powered or otherwise driven wheels at opposing ends thereof. The driven wheels are directly connected to or otherwise fixed for positive mechanical rotation with the drive axle. A control mechanism associated with the transmission assembly governs the direction of rotation of the drive axle, and hence, the direction of travel of the vacuum cleaner. The control mechanism is typically actuated by articulating or pivoting the upright handle portion of the vacuum cleaner relative to the floor nozzle to effectuate either forward or reverse travel of the vacuum cleaner.

[0003] One problem associated with the illustrated drive arrangement is that when the upright handle portion is pivoted about the floor nozzle portion, the direct mechanically coupling of the electric motor output shaft to the drive wheels results in an abrupt or sudden start or acceleration of the vacuum cleaner in either the forward or reverse directions. Such “jump starts” can be disturbing to the user during a vacuuming operation.

[0004] Accordingly, it has been considered desirable to develop a new and improved drive wheel assembly for a self-propelled vacuum cleaner that meets the above-stated needs and overcomes the foregoing difficulties and others while providing better and more advantageous results.

SUMMARY OF THE INVENTION

[0005] In accordance with one aspect of the present invention, a wheel assembly is disclosed for a vacuum cleaner that has a drive axle mechanically coupled to a drive source. The wheel assembly includes a drive member rotatably secured to the drive axle, a wheel casing at least partially surrounding the drive member, and a resilient coupling that establishes a rotational engagement between the drive member and the wheel casing after a predetermined amount of rotation of the drive member relative to the wheel casing.

[0006] In accordance with another aspect of the present invention, a self-propelled vacuum cleaner is disclosed. The self-propelled vacuum cleaner includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly including a drive member rotatably secured to the drive axle, an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing.

[0007] In accordance with yet another aspect of the present invention, a method is disclosed for propelling a vacuum cleaner that includes a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly having a drive member rotatably secured to the drive axle, an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing. The method includes rotating the drive axle and the drive member while maintaining the outer wheel casing stationary for a predetermined period of time, and establishing a positive rotational engagement between the drive member and the outer wheel casing after the predetermined period of time has elapsed to cause the outer wheel casing to rotate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the preferred embodiments of the invention and are not to be construed as limiting the same.

[0009]FIG. 1 is a front elevational view of an exemplary upright vacuum cleaner that incorporates a drive wheel assembly according to the present invention;

[0010]FIG. 2 is an enlarged, exploded view of a first embodiment of the drive wheel assembly of FIG. 1 from a first perspective;

[0011]FIG. 3 is an exploded view of the drive wheel assembly of FIG. 2 from a second perspective;

[0012]FIG. 4 is an exploded view of the drive wheel assembly of FIG. 2 from a third perspective;

[0013]FIG. 5 is a side elevational view of the drive wheel assembly of FIG. 2 in an assembled configuration;

[0014]FIG. 6 is a section view of the drive wheel assembly of FIG. 5 taken along line 6-6;

[0015]FIG. 7 is a section view of the drive wheel assembly of FIG. 6 taken along line 7-7;

[0016]FIG. 8 is a section view of the drive wheel assembly of FIG. 5 taken along line 8-8;

[0017]FIG. 9 is a side elevational view of a second embodiment of a drive wheel assembly according to the present invention;

[0018]FIG. 10 is a section view of the drive wheel assembly of FIG. 9 taken along the line 10-10; and

[0019]FIG. 11 is an exploded perspective view of the drive wheel assembly of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiments of the invention only and not for purposes of limiting same, FIG. 1 shows an exemplary upright vacuum cleaner housing A having an upright handle assembly B including a dirt holding chamber, and a floor nozzle assembly C. The upright handle assembly B is joined to the floor nozzle assembly C by conventional pivot means D. In the embodiment being described, the floor nozzle assembly C includes two powered or otherwise driven wheel assemblies 10 and two non-powered wheel or caster assemblies 12. While the vacuum cleaner A is illustrated as being of an upright type, it should be appreciated by those of average skill in the art that the wheel construction illustrated herein can also be employed for use on canister-type vacuum cleaners, wet/dry vacuum cleaners, carpet extractors, etc., and in a variety of other wheeled environments.

[0021] With reference now to FIG. 2, each wheel assembly 10 includes a drive member 14, a wheel housing 16, and a wheel housing cover 18. The wheel housing 16 and the wheel cover 18 can be collectively referred to as an outer wheel casing. The wheel housing 16 is formed from a cylindrical side wall 20 and, as best shown in FIG. 3, a disk-shaped end wall 22. Located on a free edge of the cylindrical side wall 20 is an annular flange 24. With continued reference to FIG. 3, a central aperture 26 extends through the end wall 22. Referring to FIG. 4, the aperture 26 is adapted to receive a bearing 28. In the embodiment being described, the bearing 28 is an oil impregnated, sintered bronze radial bearing.

[0022] Referring again to FIG. 2, the wheel cover 18 is formed as a circular disk having a cylindrical side wall 30, an outer surface 32 a, and, as shown in FIG. 4, an inner surface 32 b. With continued reference to FIG. 4, an annular slot 34 is defined in the inner surface 32 b proximate the side wall 30. With reference to FIG. 7, the slot 34 is sized and shaped to accommodate the annular flange 24 of the wheel housing 16 in an assembled state of the wheel assembly 10. As such, the wheel housing 16 and the wheel cover 18 cooperate to enclose or otherwise surround the drive member 14. Referring again to FIGS. 2 and 3, a central aperture 36 extends through the center of the wheel cover 18. The aperture 36 is adapted to receive a bearing 38 such as an oil impregnated, sintered bronze radial bearing.

[0023] With continued reference to FIGS. 2-4, the drive member 14 is generally formed as a spool or reel with first and second disk-shaped end walls 40, 42 and a reduced-diameter cylindrical portion 44 located between them. As such, a circumferential channel or groove 45 is defined in the member 14. Further, a central aperture 46 extends axially through the member 14. As shown in FIG. 2, a transverse groove or channel 48 is defined in the first end wall 40. The transverse groove 48 communicates with the aperture 46. As shown in FIG. 4, an arcuate or C-shaped (i.e. semi-circular) groove or channel 50 is defined in the second end wall 42.

[0024] The drive member 14 is coupled to the wheel housing 16 and wheel cover 18 by a resilient coupling including a resistance means. In the embodiment being described, the resistance means takes the form of at least one, and preferably two or more, elastic members 52, 54 such as coil springs and the like. As best shown in FIG. 6, each coil spring 52, 54 includes fastening means associated with each end thereof. The fastening means takes the form of inner and outer hook-shaped end portions 56, 58, respectively of each coil spring. The inner hook portion 56 of each spring is retained within the annular groove 45 by a transverse pin 60 that extends through corresponding apertures 62 associated with each end wall 40, 42. The apertures 62 are spaced approximately 180° apart. Likewise, the outer hook portion 58 of each spring is supported by a transverse pin 64 that extends through corresponding apertures 66 associated with the wheel housing 16 and the wheel cover 18. The apertures 66 are also spaced approximately 180° apart.

[0025] As best shown in FIG. 3, a wheel drive pin 68 is mounted in an aperture 70 associated with the wheel housing end wall 22. A free end of the wheel drive pin 68 projects into the arcuate channel 50 associated with the end wall 42 in an assembled state of the wheel assembly 10.

[0026] Referring again to FIG. 2, the radial bearings 28, 38 and the aperture 46 are axially aligned to rotatably support a drive axle 72 of the vacuum cleaner A. As best shown in FIG. 7, a free end of the drive axle 72 includes a transverse notch 74 that accommodates a drive pin or key 76 positioned within the channel 48 associated with the end wall 40. Accordingly, the drive pin 76 transfers power from the drive axle 72 to the drive member 14 during operation of the vacuum cleaner.

[0027] Referring now to FIG. 8, in a “resting” or equilibrium state of the wheel assembly 10 (i.e. the drive axle 72 is not applying rotational power to the drive member 14), there is minimal or no spring force generated by the springs 52, 54, and the free end of the wheel drive pin 68 is substantially centered along the length of the arcuate notch 50 in the end wall 42.

[0028] Power is directly coupled from the drive axle 72 to the drive member 14, via the drive pin 76, when the vacuum cleaner drive control mechanism is actuated (such as by pivoting the vacuum cleaner upright handle portion C forward or backward relative to the floor nozzle portion B). During initial rotation of the drive member 14, the depending arcuate notch 50 rotates relative to the stationary wheel drive pin 68, and the elastic members 52, 54 are increasingly tensioned or otherwise stretched to apply a gradually increasing torque force to the outer wheel casing.

[0029] Continued rotation of the drive member 14 results in driving an end wall of the arcuate notch 50 into contact with the wheel drive pin 68 against a tension force generated by the elastic members 52, 54 to effectuate a positive rotational engagement between the drive member 14 and the wheel housing 16 and wheel cover 18. The velocity with which the notch end wall impacts the wheel drive pin 68 can be controlled (i.e. reduced) by purposeful selection of the elastic characteristics of the elastic members 52, 54.

[0030] It is recognized that the gradual application of torque results in a less abrupt acceleration of the vacuum cleaner. That is, a predetermined time period elapses from the instant that the drive control mechanism is actuated to the point that positive rotational engagement of the outer wheel casing is established. During this time period, the elastic members are gradually tensioned and a torque force is gradually applied to the outer wheel casing. Accordingly, actuation of the drive wheel assembly 10 in response to an input from the vacuum cleaner drive control mechanism is controlled by i) providing a delay interval from the moment that the drive control mechanism is actuated, and ii) gradually increasing a torque force to the outer wheel casing to the point that a positive rotational engagement is established.

[0031] It is further recognized that a certain amount of backlash (such as with a clutch, etc.) can be designed into vacuum cleaner drive train (including the drive wheel assembly) so that when power to the drive axle 72 is suspended (such as when moving the vacuum cleaner drive control mechanism from a first drive position—such as forward—to a neutral position, or through the neutral position to a second drive position—such as backward), a centering force is generated by the springs 52, 54. The centering force causes the drive member 14 to slightly rotate relative to the outer wheel casing thereby repositioning (i.e. centering) the inner arcuate channel 50 relative to the wheel drive pin 68. Thereafter, a subsequent actuation of the drive control mechanism results in establishing a time-delayed and less abrupt engagement of the drive wheel assemblies 10 as described above.

[0032] It is contemplated that each of the drive member 14, wheel housing 16, wheel cover 18, and associated pins 60, 64, 68, and 70 can be manufactured (e.g. molded, cast, turned, stamped, machined, cut, etc.) from suitable materials, such as a plastic material, a composite material, a resin material, a metal material, a wood material, etc. Further, the side walls 20, 30 defining outer wheel casing can include a textured (e.g rubberized) surface or a layer of tread material to improve the traction of the wheel assemblies 10.

[0033] It should be recognized that suitable screws, bolts, nails, cotter pins, etc. can be used in place of any one or more of the pins 60, 64, 68, and 70. The springs 52, 54 are preferably formed from steel. It should also be recognized that resistance means other than coil springs 52, 54 can be utilized to reduce the velocity with which the drive member 14 impacts the wheel drive pin 68 to establish positive rotational engagement.

[0034] Further, it should be recognized that if the tension forces generated by the stretched springs 52, 54 are strong enough, it is possible that a rotational connection between the drive member and the wheel housing can be established by the springs alone without the positive rotational engagement that is provided by the channel 50 and the wheel drive pin 68. In either case, as the springs 52, 54 are increasingly tensioned, torque is gradually applied to the outer wheel casing.

[0035] A further embodiment of a driven wheel assembly 110 according to the present invention is shown in FIGS. 9-11, where reference numerals offset by a factor of 100 are used to denote the same or similar components of the wheel assembly 10 described and illustrated in FIGS. 1-8.

[0036] With particular reference now to FIG. 11, the wheel assembly 110 includes a drive member 114, a wheel housing 116, and a wheel housing cover 118. The wheel housing 116 and the wheel cover 118 is collectively referred to as an outer wheel casing. The wheel housing 116 is formed from a cylindrical side wall 120 and a disk-shaped end wall 122 that cooperate to define a contoured open cavity 180. A central aperture (such as e.g. 26, FIG. 3) extends through the end wall 122 and is sized and shaped to receive at least one of a radial bearing 128 and a radial fluid seal 182 (in the case of one embodiment of the invention described further below).

[0037] A plurality of projections 184 are formed integral with the cylindrical side wall 120 and extend radially inward from an inner surface thereof within the open cavity 180. As best shown in FIG. 10, in the embodiment being described, four projections 184 are circumferentially-spaced approximately 90° apart from each other to define four chamber portions 186 that generally converge at a central cavity portion 188. The width of each projection 184 tapers in a radially inward direction, and the side surface of each projection is shaped or otherwise contoured to define a land or seat 190.

[0038] Referring again to FIG. 11, the wheel cover 118 is formed as a circular disk. A central aperture 136 through the cover 118 is adapted (i.e. sized and shaped) to receive at least one of a bearing 138 (such as an oil impregnated, sintered bronze radial bearing) and a second fluid seal 182. (FIG. 9). It is contemplated that the wheel cover 118 can include a cylindrical side wall (e.g. 30, FIG. 4) with an annular slot (e.g. 34, FIG. 4) that is sized and shaped to accommodate an annular flange (such as e.g. 24, FIG. 4) of the wheel housing to enclose and/or seal the drive member 114 within the housing cavity 180. Alternatively, the wheel cover 118 can mate with a planar open end surface of the wheel housing 116 and be positively secured thereto with conventional attachment means such as nuts, bolts, screws, adhesive, threads, etc. In both cases, a gasket (not shown) can be interposed between the wheel cover 118 and the open end surface of the wheel housing 116 to provide a fluid-tight seal therebetween.

[0039] With continued references to FIGS. 10 and 11, the drive member 114 is generally formed as an impeller with a plurality of vanes 192 extending radially outward from a central hub 194. A passage or aperture 146 extends axially through a side wall defining the central hub 194. In the embodiment being described, four vanes 192 are circumferentially-spaced approximately 90° apart from each other. The width of each vane 192 tapers in a radially inward direction, and the side surface of each vane is shaped or otherwise contoured to define a land or seat 196.

[0040] Referring again to FIG. 9, in an assembled state of the Gwheel assembly 110, the fluid seals 182 and/or radial bearings 128, 138 are axially aligned with the drive hub passage 146 and rotatably support a drive axle 172 of the vacuum cleaner. The drive member 114 is rotatably secured to, or otherwise fixed for rotation with, the drive axle 172. The drive axle 172 can be splined, threaded, keyed, etc. to fixedly secure the drive member 114 to the axle 172. As best shown in FIG. 10, the wheel housing chamber portions 186 each accommodate a respective drive member vane 192 while the central cavity portion 188 of the wheel housing 116 accommodates the drive member central hub 194. The drive member 114 is coupled to the wheel housing 116 by a resilient coupling including at least one of a resistance means and a damping means.

[0041] In the embodiment being described, the resistance means takes the form of at least one, and preferably two or more (e.g. four), elastic members 152 such as coil springs and the like, and the damping means takes the form of at least one, and preferably two or more (e.g. four), damping members 198 such as dashpots and the like. The damping means can also take the form of a fluid 200 within the cavity 180. In such as case, the seals 182 prevent such fluid from leaking from the cavity 180. It should be appreciated that, within a specified operating range, the elastic members 152 provide a directly proportional and substantially linear resistance versus displacement characteristic, whereas the damping members 198 or damping fluid 200 provide a directly proportional and substantially linear resistance versus velocity characteristic.

[0042] Each of the at least one elastic members 152 is interposed between the mutually opposed lands 190, 196 of the wheel housing projections 184 and drive member vanes 192, respectively. It is contemplated that the lands 190, 196 can be recessed or otherwise bored to retain respective ends of a coil spring. Alternatively, a retainer pin(s) 202 can project from one or both lands 190, 196 to hold a coil spring in place between a projection 184 and an adjacent drive member vane 192. Likewise, each of the at least one damping members 198 is interposed between the mutually opposed lands 190, 196 of the projections 184 and drive member vanes 192, respectively. It is contemplated that the lands 190, 196 can be recessed or otherwise bored to retain respective ends of a damping member. Further, maintaining the elastic members 152 and damping members 198 in slight compression at a resting state of the wheel assembly 110 assists in maintaining the position of the respective elastic and damping members 152, 198 between the drive member 114 and wheel housing 116.

[0043] It is contemplated that the wheel assembly 110 can be configured with at least two elastic members 152, or with at least two damping members 198, or preferably, with a combination of elastic members 152 and damping members 198. For instance, in the embodiment illustrated in FIG. 10, the wheel assembly 110 includes four elastic members 152 and four damping members 198 with i) a first chamber portion 186 housing two elastic members 152 on opposing sides of a first drive member vane 192, ii) a second chamber portion 186 housing two damping members 198 on opposing sides of a second drive member vane 192, and iii) third and fourth chamber portions 186 housing an elastic member 152 and a damping member 198 on opposing sides of third and fourth drive member vanes 192, respectively.

[0044]FIG. 10 illustrates a resting or equilibrium state of the wheel assembly 110. That is, the drive axle 172 is not applying rotational power to the drive member 114. Accordingly, there are no tension forces and compression forces, or at least minimal and substantially equal tension forces and compression forces, generated by the elastic members 152 and damping members 198 such that the drive member vanes 192 are substantially centered within the respective wheel housing chamber portions 186. A rotational force is directly coupled from the drive axle 172 to the drive member 114 when the vacuum cleaner drive control mechanism is actuated (such as by pivoting the vacuum cleaner upright handle portion C forward or backward relative to the floor nozzle portion B).

[0045] During initial rotation of the drive member 114, the elastic members 152 and damping members 198 located on the leading edge of each drive member vane 192 are compressed, while the elastic members 152 and damping members 198 located on a trailing edge of each drive member vane 192 are tensioned. Continued rotation of the drive member 114 results in gradually increasing the compressive and tensile forces acting on the elastic members 152 and/or the damping members 198, and hence a gradually increasing torque force acting on the wheel housing until a positive rotational engagement between the drive member 114 and the wheel housing 116 is established. This generally occurs when the rotational driving force acting on the drive member 114 overcomes the compressive and/or tensile forces generated by the elastic members 152 and/or the damping members 198.

[0046] Positive rotational engagement can occur when the leading edge elastic elements and/or damping elements are fully compressed, or can occur at some point less than full compression of the elastic elements and/or damping elements. In either case, the abruptness with which a positive rotational engagement between the drive member 114 and the wheel housing 116 is established can be controlled by purposeful selection of the elastic characteristics of elastic members 152 and of the damping characteristics of the damping members 198. Accordingly, actuation of the drive wheel assembly 110 in response to an input from the vacuum cleaner drive control mechanism is controlled by gradually applying a torque force to the wheel housing 116 over a predetermined period of time.

[0047] Referring again to FIG. 10, the damping means can be a fluid within the housing cavity 180. In such case the level of damping provided by such fluid can be regulated by i) the viscosity of the damping fluid, and/or ii) throttling the flow of fluid within the cavity 180, such as through one or more channels 210 defined between the ends of each drive member vane 192 and the inner surface of housing side wall 120, and/or through one or more channels 212 defined between the ends of each housing projection 184 and the drive member center hub 194.

[0048] The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. 

What is claimed is:
 1. A wheel assembly for a vacuum cleaner having a drive axle mechanically coupled to a drive source, the wheel assembly comprising: a drive member rotatably secured to the drive axle; a wheel casing at least partially surrounding the drive member; and a resilient coupling that establishes a rotational engagement between the drive member and the wheel casing after a predetermined amount of rotation of the drive member relative to the wheel casing.
 2. The wheel assembly of claim 1, wherein the resilient coupling includes a resistance means and a damping means, the resistance means exhibiting a linear resistance versus displacement characteristic and the damping means exhibiting a linear resistance versus velocity characteristic.
 3. The wheel assembly of claim 1, wherein the resilient coupling includes at least one of a resistance means and a damping means, the resistance means exhibiting a linear resistance versus displacement characteristic and the damping means exhibiting a linear resistance versus velocity characteristic.
 4. The wheel assembly of claim 1, wherein the resilient coupling includes at least one elastic member secured to the drive member and the wheel casing, the elastic member exhibiting a linear resistance versus displacement characteristic.
 5. The wheel assembly of claim 1, wherein the resilient coupling includes at least one coil spring having a first end secured to the drive member and a second end secured to the wheel casing.
 6. The wheel assembly of claim 1, wherein the resilient coupling includes at least one damping member secured between the drive member and the wheel casing, the damping member exhibiting a linear resistance versus velocity characteristic.
 7. The wheel assembly of claim 1, wherein the resilient coupling includes at least one dashpot having a first end secured to the drive member and a second end secured to the wheel casing.
 8. The wheel assembly of claim 1, wherein the wheel casing includes a wheel housing having a cavity that accommodates the drive member, the cavity having a plurality of projections that cooperate to define a plurality of chamber portions, and the drive member having a plurality of vanes each positioned within a respective chamber portion.
 9. The wheel assembly of claim 8, wherein the resilient coupling includes at least one coil spring positioned between one of the plurality of drive member vanes and one of the plurality of projections.
 10. The wheel assembly of claim 9, wherein the resilient coupling further includes at least one dashpot positioned between another one of the plurality of drive member vanes and another one of the plurality of projections.
 11. The wheel assembly of claim 8, wherein the resilient coupling includes at least one dashpot positioned between one of the plurality of drive member vanes and one of the plurality of projections.
 12. The wheel assembly of claim 1, wherein the wheel casing includes a wheel housing having a cavity that accommodates the drive member and a wheel cover that encloses the cavity, the drive member includes first and second disk-shaped end walls separated by a reduced diameter cylindrical portion that defines a channel, and the resilient coupling includes at least one elastic member having a first end secured to the drive member within the channel and a second end that is fixed for rotation with the wheel casing.
 13. The wheel assembly of claim 12, wherein the resilient coupling further includes an arcuate groove defined in the first disk-shaped end wall, and a drive pin fixed for rotation with the wheel casing, a free end of the drive pin extending into the arcuate groove, the drive member rotating into abutment with the drive pin to establish a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing.
 14. A self-propelled vacuum cleaner comprising: a drive motor; a drive axle coupled to the drive motor; and at least one drive wheel assembly including a drive member rotatably secured to the drive axle, an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing.
 15. The vacuum cleaner of claim 14, wherein the resilient coupling includes at least one spring linking the drive member to the outer wheel casing.
 16. The vacuum cleaner of claim 15, wherein the resilient coupling further includes at least one dashpot linking the drive member to the outer wheel casing.
 17. The vacuum cleaner of claim 14, wherein the wheel casing includes a wheel housing having a cavity that accommodates the drive member, the cavity having a plurality of projections that cooperate to define a plurality of chamber portions, and the drive member having a plurality of vanes each positioned within a respective chamber portion.
 18. The vacuum cleaner of claim 17, wherein the resilient coupling includes at least one coil spring positioned between one of the plurality of drive member vanes and one of the plurality of projections.
 19. The vacuum cleaner of claim 18, wherein the resilient coupling further includes at least one dashpot positioned between another one of the plurality of drive member vanes and another one of the plurality of projections.
 20. The vacuum cleaner of claim 17, wherein the resilient coupling includes at least one dashpot positioned between one of the plurality of drive member vanes and one of the plurality of projections.
 21. The vacuum cleaner of claim 14, wherein the wheel casing includes a wheel housing having a cavity that accommodates the drive member and a wheel cover that encloses the cavity, the drive member includes first and second disk-shaped end walls separated by a reduced diameter cylindrical portion that defines a channel, and the resilient coupling includes at least one elastic member having a first end secured to the drive member within the channel and a second end that is fixed for rotation with the wheel casing.
 22. The vacuum cleaner of claim 21, wherein the resilient coupling further includes an arcuate groove defined in the first disk-shaped end wall, and a drive pin fixed for rotation with the wheel casing, a free end of the drive pin extending into the arcuate groove, the drive member rotating into abutment with the drive pin to establish a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing.
 23. A method of propelling a vacuum cleaner including a drive motor, a drive axle coupled to the drive motor, and at least one drive wheel assembly having a drive member rotatably secured to the drive axle, the at least one drive wheel assembly further including an outer wheel casing surrounding the drive member, and a resilient coupling that establishes a positive rotational engagement between the drive member and the wheel casing after the predetermined amount of rotation of the drive member relative to the wheel casing, the method comprising: rotating the drive axle and the drive member while maintaining the outer wheel casing stationary for a predetermined period of time; and establishing a positive rotational engagement between the drive member and the outer wheel casing after the predetermined period of time has elapsed to cause the outer wheel casing to rotate.
 24. The method of claim 23, wherein the step of rotating includes the subsidiary step of rotating a semi-circular channel associated with the drive member about a drive pin associated with the outer wheel casing, and the step of establishing includes the subsidiary step of contacting the wheel drive pin with an end wall of the semi-circular channel.
 25. The method of claim 24, wherein the step of rotating further includes the subsidiary step of tensioning at least one spring linking the drive member to the outer wheel casing.
 26. The method of claim 23, wherein the step of rotating further includes the subsidiary step of compressing at least one elastic member linking the drive member to the outer wheel casing.
 27. The method of claim 26, wherein the step of rotating further includes the subsidiary step of tensioning at least another elastic member linking the drive member to the outer wheel casing.
 28. The method of claim 26, wherein the step of rotating step further includes the subsidiary step of compressing at least one damping member linking the drive member to the outer wheel casing.
 29. The method of claim 23, wherein the step of rotating further includes the subsidiary step compressing at least one elastic member and at least one damping member, and tensioning at least another elastic member and at least another damping member. 